package com.example.androidtest1;

import androidx.appcompat.app.AppCompatActivity;

import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;

public class Calculator extends AppCompatActivity implements View.OnClickListener {
    private Button btn_0;//0数字按钮
    private Button btn_1;//1数字按钮
    private Button btn_2;//2数字按钮
    private Button btn_3;//3数字按钮
    private Button btn_4;//4数字按钮
    private Button btn_5;//5数字按钮
    private Button btn_6;//6数字按钮
    private Button btn_7;//7数字按钮
    private Button btn_8;//8数字按钮
    private Button btn_9;//9数字按钮
    private Button btn_point;//小数点按钮
    private Button btn_clear;//clear按钮
    private Button btn_del;//del按钮
    private Button btn_plus;//+按钮
    private Button btn_minus;//-按钮
    private Button btn_multply;//*按钮
    private Button btn_divide;//除号按钮
    private Button btn_equal;//=按钮
    private EditText editText;

    boolean clear_flag;//清空标识

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_calculator);

//        绑定按钮
        btn_0 = (Button) findViewById(R.id.btn_0);
        btn_1 = (Button) findViewById(R.id.btn_1);
        btn_2 = (Button) findViewById(R.id.btn_2);
        btn_3 = (Button) findViewById(R.id.btn_3);
        btn_4 = (Button) findViewById(R.id.btn_4);
        btn_5 = (Button) findViewById(R.id.btn_5);
        btn_6 = (Button) findViewById(R.id.btn_6);
        btn_7 = (Button) findViewById(R.id.btn_7);
        btn_8 = (Button) findViewById(R.id.btn_8);
        btn_9 = (Button) findViewById(R.id.btn_9);
        btn_point = (Button) findViewById(R.id.btn_point);
        btn_clear = (Button) findViewById(R.id.btn_clear);
        btn_del = (Button) findViewById(R.id.btn_del);
        btn_plus = (Button) findViewById(R.id.btn_plus);
        btn_minus = (Button) findViewById(R.id.btn_minus);
        btn_multply = (Button) findViewById(R.id.btn_multply);
        btn_divide = (Button) findViewById(R.id.btn_divide);
        btn_equal = (Button) findViewById(R.id.btn_equal);
        editText = (EditText) findViewById(R.id.et_input);

//        绑定事件
        btn_0.setOnClickListener(this);
        btn_1.setOnClickListener(this);
        btn_2.setOnClickListener(this);
        btn_3.setOnClickListener(this);
        btn_4.setOnClickListener(this);
        btn_5.setOnClickListener(this);
        btn_6.setOnClickListener(this);
        btn_7.setOnClickListener(this);
        btn_8.setOnClickListener(this);
        btn_9.setOnClickListener(this);
        btn_point.setOnClickListener(this);
        btn_clear.setOnClickListener(this);
        btn_del.setOnClickListener(this);
        btn_plus.setOnClickListener(this);
        btn_minus.setOnClickListener(this);
        btn_multply.setOnClickListener(this);
        btn_divide.setOnClickListener(this);
        btn_equal.setOnClickListener(this);
    }

    @Override
    public void onClick(View view) {
        String input = editText.getText().toString();
        switch (view.getId()){
            case R.id.btn_0:
            case R.id.btn_1:
            case R.id.btn_2:
            case R.id.btn_3:
            case R.id.btn_4:
            case R.id.btn_5:
            case R.id.btn_6:
            case R.id.btn_7:
            case R.id.btn_8:
            case R.id.btn_9:
            case R.id.btn_point:
                if(clear_flag){
                    clear_flag = false;
                    editText.setText("");
                }
                editText.setText(input + ((Button)view).getText());
                break;
            case R.id.btn_plus:
            case R.id.btn_minus:
            case R.id.btn_multply:
            case R.id.btn_divide:
                if(clear_flag){
                    clear_flag = false;
                    input = "";
                    editText.setText("");
                }
                editText.setText(input + " " + ((Button)view).getText() + " ");
                break;
            case R.id.btn_clear:
                clear_flag = false;
                input = "";
                editText.setText("");
                break;
            case R.id.btn_del:
                if(clear_flag){
                    clear_flag = false;
                    input = "";
                    editText.setText("");
                }else if(input != null || !input.equals("")) {
                    editText.setText(input.substring(0, input.length() - 1));
                }
                break;
            case R.id.btn_equal:
                getResult();
                break;
        }
    }
    //运算结果
    private void getResult(){
        String exp = editText.getText().toString();
        if(exp==null||exp.equals(""))
            return;
        if(!exp.contains(" "))
            return;
        if(clear_flag){
            clear_flag = false;
            return;
        }
        clear_flag = true;
        double result = 0;
        //运算符前的数字
        String s1 = exp.substring(0,exp.indexOf(" "));
        //运算符
        String op = exp.substring(exp.indexOf(" ")+1,exp.indexOf(" ")+2);
        //运算符后的数字
        String s2 = exp.substring(exp.indexOf(" ")+3);

        if(!s1.equals("")&&!s2.equals("")) {
            double d1 = Double.parseDouble(s1);
            double d2 = Double.parseDouble(s2);
            if (op.equals("+")) {
                result = d1 + d2;
            } else if (op.equals("-")) {
                result = d1 - d2;
            } else if (op.equals("*")) {
                result = d1 * d2;
            } else if (op.equals("/")) {
                if (d2 == 0)
                    result = 0;
                else
                    result = d1 / d2;
            }

            if (!s1.contains(".") && !s2.contains(".") && !op.equals("/")) {
                int r = (int) result;
                editText.setText(r + "");
            } else
                editText.setText(result + "");
        }else if(!s1.equals("") && s2.equals("")){
            editText.setText(exp);
        }else if(s1.equals("") && !s2.equals("")){
            double d2 = Double.parseDouble(s2);
            if (op.equals("+")) {
                result = 0 + d2;
            } else if (op.equals("-")) {
                result = 0 - d2;
            } else if (op.equals("*")) {
                result = 0;
            } else if (op.equals("/")) {
                result = 0;
            }

            if (!s1.contains(".") && !s2.contains(".")) {
                int r = (int) result;
                editText.setText(r + "");
            } else
                editText.setText(result + "");
        }else {
            editText.setText("");
        }

    }
}